Content Protection (CP) systems are well known for providing protection of audio-visual (A/V) content. Typically, a content protection system includes a source device (e.g., set top box (STB), digital videocassette (DVCR or DVHS) player, digital versatile (or video) disc (DVD) player, etc.) and a sink device (e.g., digital television (DTV), etc.). As will be understood by those skilled in the art, the ‘source’ device is so named because it provides a source of A/V content. Similarly, the ‘sink’ device provides a medium for viewing the A/V content. In order to prevent multiple viewing of certain A/V content, a content protection system is typically installed between the source and he sink device. For example, in the case of a certain program recorded using a DVCR, the CP system will prevent viewing of the program beyond the limits set by the provider of the program (e.g., copyright holder). For instance, the provider may permit the program to be watched once, but not thereafter. In such a case, the CP system would prevent viewing of the program on the sink device (e.g., DTV) if the user attempts to play the program through the DVCR more than once.
Some commercially available products have recording systems which permit a function commonly known as ‘video pause’ mode (e.g., TiVO, etc.). These products are often referred to as Personal Video Recorders (PVRs). In some instances, a PVR may be integrated into a television or other apparatus to allow ‘video pause’ of the television picture. In operation, a ‘live’ A/V stream enters the television for viewing. This live A/V stream is transmitted to a recording device operating in a passive mode (e.g., computer memory, etc.) in the television before it is presented on the display screen of the television. Initially, the recording device operates only as ‘pass-through’, and passes the content stream on to the display screen unaltered, while at the same time making a copy of the content stream. When the user selects the ‘video pause’ function the output of the recording device is no longer sent to the display screen, but the recording continues. When the user deselects the ‘video pause’ function (i.e., ‘unpauses’ the television), the content stream from the recording device to the display screen resumes from the paused location, and the recording continues. The content stream viewed by the user is now delayed by the amount of the pause time. At this point, the user has the option of either watching the time delayed content stream, or ‘catching up’ with the live content stream by skipping portions of the recorded content stream. Consumers appreciate this feature as it allows them to carry out other tasks without having to miss portions of a live broadcast (e.g., you can go make a sandwich during a live football game and not miss a second of the action).
Another feature of PVRs is the ability to perform an ‘instant replay’ function (the playing of the same portion of content over and over again). Thus, if a user wished to watch a pivotal play in a football game over again several time to determine if the referee made a good call, the PVR typically permits the storing of content for this function as well.
However, ‘video pause’ and ‘instant replay’ functionality present several problems as well. Content providers desire to sell their most valuable content on a ‘view only’ basis (i.e., no recordings are permitted). By the same token, the content providers may want to control what functionality is allowed to consumers, for example, allowing a ‘video pause’ function, but preventing an ‘instant replay’ function.
Present solutions to this problem include licensing television manufacturers and prohibiting storage of the content for more than a specified period of time. For example, the ‘video pause’ recorder would only store the bit stream for a maximum of twenty four (24) hours. After the specified time period has expired, the recording device automatically erases the recording. This solution is problematic because if the recording device is hacked in the interim period (e.g., within 24 hours), the content is available to be copied. Additionally, if the recording device is somehow deceived about the time, the content may be available for longer periods then intended by the content provider.
Thus, there is presently a need for a method and apparatus for copy protecting content stored during video pause mode so that the content may only be viewed in the limited manner intended by the content providers.